Predicting early recurrence after resection of initially unresectable colorectal liver metastases: the role of baseline and pre-surgery clinical, radiological and molecular factors in a real-life multicentre experience

Background Advances in surgical techniques and systemic treatments have increased the likelihood of achieving radical surgery and long-term survival in metastatic colorectal cancer (mCRC) patients with initially unresectable colorectal liver metastases (CRLMs). Nonetheless, roughly half of the patients resected after an upfront systemic therapy experience disease relapse within 6 months from surgery, thus leading to the question whether surgery is actually beneficial for these patients. Materials and methods A real-world dataset of mCRC patients with initially unresectable liver-limited disease treated with conversion chemotherapy followed by radical resection of CRLMs at three high-volume Italian institutions was retrospectively assessed with the aim of investigating the association of baseline and pre-surgical clinical, radiological and molecular factors with the risk of relapse within 6 or 12 months from surgery. Results Overall, 268 patients were included in the analysis and 207 (77%) experienced recurrence. Ninety-six (46%) of them had disease relapse within 6 months after CRLM resection and in spite of several variables associated with early recurrence at univariate analyses, only primary tumour resection at diagnosis [odds ratio (OR) 0.53, 95% confidence interval (CI) 0.32-0.89, P = 0.02] remained significant in the multivariable model. Among patients with resected primary tumours, pN+ stage was associated with higher risk of disease relapse within 6 months (OR 3.02, 95% CI 1.23-7.41, P = 0.02). One hundred and forty-nine patients (72%) had disease relapse within 12 months after CRLMs resection but none of the analysed variables was independently associated with outcome. Conclusions Clinical, radiological and molecular factors assessed before and after conversion chemotherapy do not reliably predict early recurrence after secondary resection of initially unresectable CRLMs. While novel markers are needed to optimize the cost/efficacy balance of surgical procedures, CRLM resection should be offered as soon as metastases become resectable during first-line chemotherapy to all patients eligible for surgery.


INTRODUCTION
Metastatic colorectal cancer (mCRC) is a fatal disease in the vast majority of cases.However, patients with colorectal liver metastases (CRLMs) may be eligible for metastases resection achieving long-term disease remission and survival. 1Liver-limited disease occurs in around 20%-30% of mCRC patients, and 10%-20% of them are deemed upfront resectable while 30%-40% are initially unresectable but potentially amenable for surgery if tumour shrinkage is achieved by conversion chemotherapy. 2,35][6][7] However, although 20%-30% of resected patients can achieve a long-term overall survival benefit from liver metastasectomy, 8 most patients relapse during the first 2 years after hepatectomy, 9,10 with about 35%-45% of early recurrences occurring within 6 months after surgery. 6,11It is not clear whether in these cases liver resection may still have a favourable impact on the subsequent steps of disease history and ultimately on patients' survival.At the same time, liver resection is encumbered by nonneglectable perioperative mortality and severe morbidity rates around 1%-3% and 30%, respectively. 12In order to maximize the risk/benefit balance of liver surgery and to avoid futile procedures, both technical/surgical and oncological/prognostic criteria should be considered. 1,13][16][17][18][19] Moreover, the impact of individual variables on the risk of early recurrence was not investigated, and potentially prognostic variables were never evaluated after the systemic therapy. 11rawing from these considerations, we assessed the risk of early recurrence according to baseline and pre-surgery clinical, radiological and molecular parameters in patients with initially unresectable liver-limited CRLMs undergoing resection after first-line chemotherapy, with the aim of building a reliable prognostic model that may support clinicians to offer liver surgery after initial systemic treatment.

Study population
Consecutive patients with resected CRLMs referred to three Italian high-volume institutions with expertise in liver surgery (Azienda Ospedaliero-Universitaria Pisana, Pisa; Veneto Institute of Oncology, Padua; Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Roma) from January 2009 to January 2022 were selected.Eligibility criteria were: R0/ R1 resection of liver metastases and primary tumour if not yet resected at the time of the beginning of conversion chemotherapy; absence of extrahepatic disease at the time of CRLM diagnosis; CRLMs deemed initially unresectable for technical and/or oncological reasons as for local multidisciplinary assessment [more than five liver metastases, 20 maximum size of the larger metastasis !5 cm, BRAFV600E mutated and technically difficult to resect; R0 resection possible with complex minor hepatectomy, 21 portal vein embolization, two-stage hepatectomy, hepatectomy combined with ablation, associating liver partition and portal vein ligation for staged hepatectomy (ALPPS), complex major hepatectomy 1,13,22,23 ]; administration of first-line treatment before liver surgery, including doublet (FOLFOX: 5-fluorouracil and oxaliplatin; CAPOX: capecitabine and oxaliplatin; FOLFIRI: 5-Fluorouracil and irinotecan) or triplet (FOLFOXIRI: 5-fluorouracil, oxaliplatin and irinotecan) plus or minus anti-vascular endothelial growth factor (anti-VEGF, bevacizumab)/epidermal growth factor receptor (anti-EGFRs, cetuximab or panitumumab) monoclonal antibodies 1,13 ; no evidence of radiological progression before surgery; availability of baseline and pre-surgery imaging [contrast-enhanced computed tomography and/or liverspecific contrast-enhanced magnetic resonance (MRI)] that were independently reviewed by radiologists with liver imaging expertise at each institution (PB and FMD for Azienda Ospedaliero-Universitaria Pisana; GR for Veneto Institute of Oncology, Padua; BB for Fondazione Policlinico Universitario Agostino Gemelli IRCCS) blinded to clinical information, treatment regimen and outcome in order to accurately evaluate the extent of hepatic disease (number and size of liver lesions, relationship of metastases with major hepatic vessels, number of hepatic segments and lobes involved at baseline and pre-surgery); and a minimum follow-up of at least 12 months after liver surgery.Radiological assessments were scheduled every 2-3 months and multidisciplinary meetings with image review were carried out after each scan in order to offer surgery as soon as the disease became resectable.The study was approved by the ethical review board of the coordinating centre (University of Pisa, ID: 3920/2013) and was conducted in accordance with the ethical principles for medical research involving human subjects adopted in the Declaration of Helsinki.

Statistical analyses
The primary objective of the present study is to identify baseline and pre-surgery clinical, radiological and molecular factors associated to early recurrence defined as the evidence of radiological disease relapse or death, whichever occurred first, within 6 months from liver surgery.Univariate and multivariate logistic regression analyses were carried out to assess the independent predictive value of clinical, radiological and molecular factors in terms of early relapse.The same analyses were carried out using a 12month cut-off for the definition of early relapse.
Descriptive statistics were used to summarise clinical, radiological and molecular prognostic characteristics.The changes in variables evaluated before and after systemic therapy (i.e. at baseline and pre-surgery) were analysed by means of Wilcoxon or McNemar tests as appropriate.Disease-free survival (DFS) was defined as the time elapsed from liver surgery to the first radiological evidence of disease relapse or death from any cause, whichever occurred first.Overall survival (OS) was defined as the time elapsed from liver surgery to death from any cause.Post-relapse OS was defined as the time elapsed from recurrence after liver surgery to death from any cause.In case of two-stage hepatectomy or staged resection of liver metastases and primary tumour, DFS and OS were calculated from the date of the last surgical procedure.Survival curves were estimated by the KaplaneMeier method and compared with the log-rank test.Hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated with a Cox proportional hazards model.The impact of clinical, radiological and molecular prognostic variables on DFS and OS was assessed by means of univariate and multivariate Cox regression analyses.
For both logistic and regression models, two parallel analyses were conducted: -Overall population, where the pT and pN variables were excluded because they were unknown for patients with unresected primary tumour at baseline.-Baseline resected primary tumour population, where the pT and pN variables were included.
Statistical significance for univariate and multivariate logistic and Cox regression analyses were set at P 0.10 and P 0.05, respectively.All analyses were carried out with R-Studio version 2022.07.02.
At baseline, liver metastases were more frequently bilobar (59%), involved more than four hepatic segments (53%) and were in contact with at least one major hepatic vessel (63%).The median size of the largest lesion was 42 mm [interquartile range (IQR) 28-65 mm, range 6-205 mm] and the median number of lesions was 4 (IQR 2-6, range 1-64).Carcinoembryonic antigen (CEA) levels were higher than 10 ng/ml in 43% of patients with a median value of 17 ng/ml (IQR 5-104 ng/ml).Baseline MRI was carried out in 34% of patients.
Overall, triplet and doublet chemotherapy were administered in 42% and 58% of patients, respectively, with the addition of a biologic agent in 91% of cases.
After a median duration of first-line treatment of 3.7 months, 75% of patients obtained a response according to RECIST criteria, with significant reductions of the median size of the largest lesions (42 versus 25 mm, P < 0.001) and median number of liver metastases (4 versus 3, P < 0.001).Patients with bilobar disease and lesions in contact with major hepatic vessels decreased after conversion chemotherapy, as well (59% versus 49%, P < 0.0001, and 63% versus 59%, P ¼ 0.04, respectively).At least one CRLM disappeared in 67% of cases.In addition, a significant reduction in CEA levels (P < 0.001) was reported.A higher number of patients underwent MRI before surgery as compared to baseline (49% versus 34%, P ¼ 0.0001).Overall, at least one preoperative (baseline and/or presurgery) MRI scan was carried out in 61% of patients.
No difference was observed between late and early recurrence in terms of site of relapse using both 6-(P ¼ 0.11) and 12-month (P ¼ 0.25) cut-offs.(Figure 1 B and C).Using a cut-off of 6 months, a longer post-relapse OS was reported in patients with late hepatic-only compared to early hepatic-only recurrence (P ¼ 0.002) and in subjects with late multiorgan relapse with respect to early multiorgan relapse (P ¼ 0.04), while no difference was observed between late extrahepatic single-organ and early extrahepatic single-organ recurrence (P ¼ 0.14) (Supplementary Figure S4 A, available at https://doi.org/10.1016/j.esmoop.2024.102991).When a cut-off of 12 months was used, a longer post-relapse OS was reported in patients with late hepatic-only compared to early hepatic-only recurrence (P ¼ 0.046) and in subjects with late extrahepatic single-organ with respect to early extrahepatic single-organ (P ¼ 0.03), while no difference was observed between late multiorgan and early multiorgan recurrence (P ¼ 0.40) (Supplementary Figure S4, panel B, available at https://doi.org/10.1016/j.esmoop.2024.102991).

DISCUSSION
Although CRLM resection is a unique chance of cure for mCRC patients, or at least it significantly enhances survival for a group of mCRC patients, roughly half of the patients relapse within 6-12 months from liver metastasectomy, thus raising concerns about the usefulness of surgery in those cases, also considering the related risk of perioperative mortality and severe morbidity. 6,11,24,25Moreover, it should be noticed that maintenance with a fluoropyrimidine plus the targeted agent initially used is a safe option, with a relatively low burden of adverse events, able to prolong the time to disease progression, with a median duration of clinical benefit of 8 months following 4-6 months of upfront combination therapy and no demonstrated survival benefit.However, our current ability to select patients with a maximized benefit from liver surgery is quite poor.Therefore, with the aim of estimating the risk of early recurrence and thus supporting clinicians and patients for the choice of the most appropriate approach in each individual patient amenable of liver resection after upfront chemotherapy, we retrospectively assessed the association of baseline and pre-surgical clinical, radiological and molecular factors with early relapse in a cohort of initially unresectable patients with liver-limited CRLMs who underwent secondary surgery at three Italian Hospitals with highvolume centres for liver surgery.
In our study, none of the investigated factors was found to be an independent predictor of 6-month recurrence, with the exception of unresected primary tumour at baseline and, among patients with resected primary tumour, pNþ stage.Even using a 12-month threshold, we failed to show any baseline and pre-surgical factor that independently correlated with the risk of early relapse.Accordingly, the multivariate Cox regression analysis did not identify any baseline or pre-surgical marker associated with improved survival to be included in a prognostic model.Only the primary tumour resection at baseline was associated with longer DFS in the overall population and BRAF mutation, and pNþ stage predicted shorter DFS among patients with resected primary tumour.In spite of apparently disappointing results, our findings actually confirm and expand a recent post hoc analysis of the Dutch CAIRO5 trial, where patients with initially unresectable CRLMs underwent bimonthly re-assessments for resectability by a central panel of experts in liver surgery during the administration of the most active first-line regimen according to international guidelines. 11Notably, despite an enormous effort for multidimensional centralized revision in a randomized trial, only the number of liver metastases before local treatment was able to predict recurrence within 6 months, 11 thus not allowing to build a predictive model of early relapse potentially useful for clinical decision making in patients candidate to liver surgery after upfront chemotherapy.Of note, although the median number of baseline liver lesions was 12 and 4 in the CAIRO5 study and in our cohort, respectively, according to the different definitions of unresectability (unresectable at baseline if an R0 resection could not be achieved in a single procedure by surgical resection versus technical/surgical and oncological/prognostic criteria), the similar results of our retrospective real-life cohort with those from the prospective investigational CAIRO5 study with comparable population size (n ¼ 268 and n ¼ 240, respectively) and frequencies of early disease relapse (36% and 43%, respectively) strengthens the reliability of our findings and the weight of oncological/prognostic factors on the probability of early relapse.Therefore, even if a median number of four liver metastases may appear too small to define our cohort as 'initially unresectable', several additional technical/surgical and oncological/prognostic criteria contribute to the definition of resectability. 1,13Indeed, most of the patients in our cohort had synchronous metastases, bilobar liver involvement with more than four hepatic segments affected, a median size of the largest lesion >40 mm, metastases in contact with at least one major hepatic vessel, RAS mutation and pathologic lymph nodes when primary tumour was resected.Unfortunately, we cannot state which specific criteria (technical, oncological or both) actually led to exclude the initial resectability in each individual case, and therefore we are not able to distinguish the impact of oncological/prognostic criteria versus technical/surgical ones in our population.Overall, our work remarks the unreliability of the current clinical, radiological and molecular featuresdevaluated either before or after chemotherapydto spare futile surgery in those patients at high risk of disease relapse after conversion chemotherapy.Notably, in our study, half of the patients with early recurrence reported a post-relapse OS longer than 27 months, thus suggesting that some patients with early recurrence still achieve benefit from liver surgery, although the potential survival benefit of metastasectomy in those patients experiencing early recurrence could not be adequately evaluated, due to the lack of a comparator arm consisting of patients not receiving secondary resection, which would be probably unethical, considering the high benefit of liver surgery.In addition, patients with early relapse, especially those experiencing single-organ recurrence, may benefit from further locoregional approaches, that were still feasible in more than one-third of the patients experiencing disease relapse within 6 months from liver surgery.Overall, survival was prolonged by LRT administered after first recurrence irrespective of the timing of relapse, thus leading to consider this approach whenever feasible.
We acknowledge some clear limitations of our study, including the retrospective design, the long timeframe of patients' inclusion, the heterogeneity of administered firstline treatments, though mostly including the same regimens administered in the CAIRO5 trial, and the availability of baseline and pre-surgical liver MRI for roughly one-third and a half of included patients, respectively.Of note, the number of variables considered in our prognostic analysis implies a risk of false-positive results intrinsic in multiple tests, anddeven more importantlydthe absence of statistical significance for the vast majority of the variables tested should be cautiously interpreted considering the risk of false-negative results.If we had applied the widely  adopted rule-of-thumb of a minimum number of events (i.e.10) for candidate predictor parameter, we would have needed a higher sample size. 26However, more flexible approaches have been proposed for clinical prediction models, 27 and our sample size (in terms of number of patients and events) can be considered adequate to estimate with enough accuracy the main outcome (the probability of early relapse).Our study also has strengths, including the revision of imaging by radiologists with liver imaging expertise and the inclusion of patients assessed in highvolume liver surgery institutions.
Considering the inaccuracy of investigated predictors for the early relapse, the most appropriate treatment option remains to offer surgery as soon as the disease becomes resectable.In addition, we endorse the adoption of novel approaches to estimate the risk of early disease relapse in the multidimensional assessment of patients with initially unresectable CRLMs.To this purpose, the longitudinal assessment of circulating tumour DNA (ctDNA) could be an ideal, non-invasive tool to track the disease load before and after conversion chemotherapy able to predict the risk of early recurrence.][35][36] Based on our findings, the secondary resection of CRLMs should be never denied to initially unresectable patients that become resectable after upfront chemotherapy.

FUNDING
The research leading to these results has received funding from the European UniondNextGenerationEU through the Italian Ministry of University and Research under PNRRdM4C2-I1.3Project PE_00000019 'HEAL ITALIA' to Chiara Cremolini CUP: I53C22001440006.The views and opinions expressed are those of the authors only and do not necessarily reflect those of the European Union or the European Commission.Neither the European Union nor the European Commission can be held responsible for them.
The study was supported by GONO and ARCO Foundations (no grant number).

Figure 1 .Volume 9 -
Figure 1.Patterns of disease recurrence.In the overall population (A) and according to timing of disease relapse, with cut-offs for early recurrence of 6 months (B) and 12 months (C).

Figure 2 .
Figure 2. Overall survival from disease relapse according to patterns of disease recurrence.CI, confidence interval; HR, hazard ratio.

Table 1 .
Patients' characteristics a McNemar test.b Paired-sample Wilcoxon test.ESMO Open R. Moretto et al.